Sol–gel preparation of NixCu1–x/silica nanocomposites using different silica precursors

The use of magnetic nanoparticles in biomedical applications has recently attracted considerable attention in fields like magnetic resonance imaging, drug delivery, and magnetic hyperthermia. Nickel–copper nanoparticles with the general formula NixCu1–x are among the most attractive materials due to their simple synthesis, high magnetization, and biocompatibility combined with a Curie temperature (TC) within the therapeutic range, making them a promising material for magnetic hyperthermia, as well as for targeted drug delivery. To avoid agglomeration and/or oxidation of such nanoparticles, they usually have to be coated with silica, noble metals, or polymers. The silica coating not only stabilizes the nanoparticles, but also improves their biocompatibility and allows further surface functionalization or drug incorporation. In this study, nanoparticles with the composition Ni67.5Cu32.5 were prepared using the sol–gel method via an in situ application of the precursor tetraethyl orthosilicate or its combination with other silica precursors, e.g., (3-aminopropyl)triethoxysilane, phenyltriethoxysilane, vinyltriethoxysilane, and bis-1,2-(triethoxysilyl)ethane. The coated nanoparticles were characterized using X-ray powder diffraction, thermogravimetric analysis, FTIR spectroscopy, magnetization measurements, transmission electron microscopy, specific surface area, and porosity (BET), and contact angle measurements. The results confirmed the absence of nonmagnetic oxides in samples, the presence of the silica coating formed from respective precursors, as well as a high potential for the use in magnetic hyperthermia. The basic characteristics of NixCu1–x nanoparticles can be varied to a certain extent with the preparation of functional coatings.